Core Viewpoint - The research reveals a conserved BBM-BAR1 regulatory module that can directly drive the fate reprogramming of microspores from gametophyte development to embryogenesis, providing a revolutionary new method for efficient in vivo haploid induction in various crops, overcoming the long-standing technical bottleneck of stress treatment [9]. Group 1 - The study demonstrates that stress treatment induces the specific expression of the transcription factor BABY BOOM (BBM) in microspores, which is sufficient to induce fate change and embryogenesis in tobacco and rice microspores, indicating BBM as a key regulatory factor in stress-induced reprogramming [5][6]. - BAR1 (BBM-activated Androgenesis Regulator 1) is identified as a new downstream effector of BBM, capable of independently initiating the embryogenesis process in microspores, similar to the role of BBM in promoting fate reprogramming [5][7]. Group 2 - Ectopic expression of BBM in microspores can trigger in vivo male gametophyte development within anthers [7]. - The expression of BBM and BAR1 can replace the need for stress treatment in inducing male gametophyte development [7]. - The conserved BBM-BAR1 module enables efficient in vivo haploid induction across various crops [7].